Light-sensitive device



' March 24, 1,942.

o. GE ISLER ETAL LIGHT SENSITIVE DEVICE Original Filed March'31, 19:54

' OQGE/SLER INVENTORSJ EISELE ATTORNEY Reissued Mar. 24, 1942 UNITED STATE LIGHT- SENSITIVE DEVICE Ottmar Geisler and Josef Eisele, Nuremberg,

Germany, assignors, by mesne assignments, to Suddeutsche Apparateiabrik Gesellscliaft m.

b. 11., Nuremberg, Germany,

Germany Original No. 2,096,170, dated PATENT OFFICE a corporation of October 19, 1937,

Serial No. 718,426, March 31, 1934. Application for reissue March 3, 1938, Serial No. In Germany April 6, 1933 2 Claims. (Cl.

This invention relates to light-sensitive devices and more particularly to light-sensitive devices having alight-permeable electrode.

An object of the invention is to improve the light-sensitive characteristics of such devices.

selenides impair the cells.

In accordance with the invention this knowledge led to the application of metals as trans- In an example of practice a light-sensitive demetal electrode either is pressed upon the photosensitive layer in the form of a very thin film vided with a transparent metal electrode. This or applied by cathode sputtering, vaporization, or

in a similar manner according to one of the known methods.

The transparent metal electrode has the task of letting through light rays, which fall uponthe photoelectric cell, to the photosensitive layer and to carry off the electrons. which are liberated when the light rays strike the cell, to the edge of the cell.

Thorough experiments have disclosed that the capacity of a blocking-layer a high degree depends upon the rectifying action of its blocking layer; the activity of the blocking layer in turn depends upon the nature of the applied coatlng electrode.

It has been found that the metals or other materials (gold, platinum, silver, etc.) known heretofore as transparent coating electrodes were not particularly well suited for producing a good blocking layer and hence a satisfactory photoelectric eflfect. Experiments have shown that the rectifying action in photoelectric cells with the known coating electrodes measured with the low voltages used for operating blocking-layer photoelectric cells is only'comparatively very small. After a short or long time these known coating electrode metals, owing to the constant contact, form chemical compounds with the photosensitive semi-conductive layer on the contact surface,

which gradually reduce the blocking-layer photoelectric effect of the cell. In photoelectric selenium cells coated with a transparent layer of gold, gold selenides are formed between the selephotoelectric cell in parent electrode .on the photosensitive layer of blocking layer photoelectric cells, particularly selenium cells, by means of which the rectifying action of the element is increased and the formation of deleterious compounds is prevented. The application of such coating electrodes produces an essentially greater power than that which was possible with the coating electrodes whichwere used heretofore for the blocking-layer photoelectric cells.

It has been found that the metals which, when applied as coating electrode on the photosensitive layer, form a good blocking layer or produce a good rectifying action of the blocking layer and do not form deleterious chemical compounds with the semi-conductive layer have a comparatively low conductivity compared with the coating layer metals known heretofore. Since the coating layer metals can be applied only as very thin films to obtain a high degree of transparency, the capacity.

of such a photoelectric cell would decrease quite considerably owing to the comparatively high voltage drop. of the photoelectric current flowingthrough the thin highly resistive coating film. In

accordance with the invention another very thin film of a metal of high conductivity is placed on top of the first coating film, by means of which a good rectifying action of the cell is obtained.

The second coating film also should be applied to the intermediate layer by cathode sputtering or vaporization according to one of the known methods. 2

Through the combination of. the two metallic coating films, placed on top .of one another, of opposite characteristics described above a blocking layer photoelectric cell is obtained which is far superior to those known heretofore in regard to capacity. The construction of blocking, layer photoelectric .cells in accordance with the invention in addition to the improved power. described also has the advantage, that by suitable choice of both metals used for the films or by sputtering accordance with the another metal and by the choice ofthe ness of each metal film the spectral sensitivity can be influenced within wide limits.

In the cells known heretofore the spectral sen sitivity was changed by placing corresponding glass or color filters in front of the cells or by coating v invention the filter action is nium and the gold layer, for example; thesethickwith a suitable lacquer. In'the cells in cell in accordance with the invention be described in the following. 7

obtained only by thetian'sparent coating films without the-additional losses in special connected filters.

The figure shows a blocking layer photoelectric I which will 'I'he'photosensitive layer, b, produced chemically or applied on a metal plate, a, as base plate.

' The transparent metal electrode, c, of a metal of low conductivity, which. with the photosensitive layer. b, forms a good blocking layer, is sputtered or evaporated on the photosensitive layer, 1). Another transparent metal electrode, d, of" high conductivity is sputtered or evaporated on the transparent intermediate electrode, 0; this electrode, d, upon illumination ofthe cell in the direction of the arrow carries the electrons- ,emerging from the blocking layer to the contact selenium and a light-permeable layer covering ing layer, 1. The layer c, consists of the metal cadmium and the layer, d, ot gold. The contact ring, e, is of copper and plate, a, of copper. or iron.

Various modifications of the invention diflFer-' ing from the specific embodiment disclosed h :ein come within the purview of this invention, the scope of which is defined in the appended claims.

What is claimed is: 1. A light sensitive device comprising a metallic base coated with a layer of light-sensitive said selenium consisting primarily of the product of the successive deposit on said selenium of cadmium and a relatively chemically inactive metal.

2. The process of making a light sensitive electric device comprising the following steps; coat- I ing one side of a metallic base plate with a layer of light sensitive material, applying a thin coatri'ng, e. The blocking layer between the photosensitive layer b, and the metal layer, 0, is repre- 4 sented by the layer, 1'.

In the preferred embodiment of the invention the photosensitive layer, b, consists oi selenium treated in well known manner toi'orm a blocking of cadmium to said light sensitive material, and applying to the cadmium a coating or a relatively chemically inacting metal or a specific conductivity higher than that of cadmium.

OTIMAR GEISLER. JOSEPH EISELE. 

